The nature and fate of individual oocyte mRNA sequences will be examined through the use of cloned mRNA probes. Globin mRNA sequences will be searched for by Northern gel analysis using globin cDNA clones, as well as searching for R loops by RNA excess hybridization and electromicroscopy. Ribosomal protein cDNA clones will be identified by virtue of mRNA hybridization and subsequent analysis of the in vitro translation product. These ribosomal protein cDNA clones will be utilized to see if the abundance of ribosomal protein mRNAs changes during oogenesis, in contrast to most random oocyte cDNA clones we have examined by comparing the mRNA distribution between oocyte polysomes and stored mRNP. The fate of oocyte mRNA sequences subsequent to fertilization will be examined by Northern gel analysis on embryo RNAs using individual cDNA clones in order to determine if any general rules exist as the to behavor of these maternal mRNA sequences during embryogenesis. Finally, injection of GTP into oocytes will be utilized in order to examine the nature of oocyte mRNA synthesis. Does it turn over quickly? Is it associated specifically with polyribosomes, or is most of the labelled poly (A) plus RNA detected mitochondrial in origin?